Impact of mountain pine beetle induced mortality on forest carbon and water fluxes
Impact of mountain pine beetle induced mortality on forest carbon and water fluxes
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DOI：
10.1088/1748-9326/9/10/105004
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发表时间：
2014-10
影响因子：
6.7
通讯作者：
David E Reed;B. Ewers;E. Pendall
中科院分区：
文献类型：
--
作者：
David E Reed;B. Ewers;E. Pendall
量化生态干扰对生态系统碳和水通量的影响将提高对生物圈-大气反馈的预测性理解。树木死亡率引起的山松树树皮甲虫（Dendroctonus ponderosae）的假设，以减少光合作用和水通量的大气中，同时增加呼吸率成正比的死亡率。这项工作使用的数据，从一个涡协方差通量塔在树皮甲虫出没的黑松（松扭叶松）森林，以测试生态系统的反应，在爆发。分析了扰动和环境因子（太阳辐射、土壤含水量和水汽压亏缺）对土壤碳（C）和水通量的影响。最大的CO2吸收量没有改变树断面积死亡率增加30%至78%，超过三年的甲虫干扰。生长季蒸散量随年份而变化，而生态系统水分利用效率（CO2净吸收与水汽损失的比率）没有变化。在2009年至2011年期间，冠层水传导率从98.6增加到151.7 mmol H2O m−2 s−1。生态系统光合作用的光利用效率增加，量子产额增加了16%，在爆发期间，随着成熟树冠以下的光照增加，剩余的植被被更多地照亮。整体净生态系统生产力与水通量，因此水的可用性。平均每周生态系统呼吸，来自光响应曲线和标准Ameriflux协议的CO2通量划分为呼吸和总生态系统生产力，死亡率增加，没有变化。呼吸作用和光合作用效率增加的单独效应在很大程度上相互抵消，可能是由于冠层中的漫射光增加和土壤有机质分解导致净CO2交换没有变化。这些结果与文献中的一个新兴共识一致，表明大规模干扰事件后的CO2和H2O动态不仅取决于树木死亡率，而且还取决于剩余的和新的植被响应，因为死亡率和恢复同时发生。
Quantifying impacts of ecological disturbance on ecosystem carbon and water fluxes will improve predictive understanding of biosphere—atmosphere feedbacks. Tree mortality caused by mountain pine bark beetles (Dendroctonus ponderosae) is hypothesized to decrease photosynthesis and water flux to the atmosphere while increasing respiration at a rate proportional to mortality. This work uses data from an eddy-covariance flux tower in a bark beetle infested lodgepole pine (Pinus contorta) forest to test ecosystem responses during the outbreak. Analyses were conducted on components of carbon (C) and water fluxes in response to disturbance and environmental factors (solar radiation, soil water content and vapor pressure deficit). Maximum CO2 uptake did not change as tree basal area mortality increased from 30 to 78% over three years of beetle disturbance. Growing season evapotranspiration varied among years while ecosystem water use efficiency (the ratio of net CO2 uptake to water vapor loss) did not change. Between 2009 and 2011, canopy water conductance increased from 98.6 to 151.7 mmol H2O m−2 s−1. Ecosystem light use efficiency of photosynthesis increased, with quantum yield increasing by 16% during the outbreak as light increased below the mature tree canopy and illuminated remaining vegetation more. Overall net ecosystem productivity was correlated with water flux and hence water availability. Average weekly ecosystem respiration, derived from light response curves and standard Ameriflux protocols for CO2 flux partitioning into respiration and gross ecosystem productivity, did not change as mortality increased. Separate effects of increased respiration and photosynthesis efficiency largely canceled one another out, presumably due to increased diffuse light in the canopy and soil organic matter decomposition resulting in no change in net CO2 exchange. These results agree with an emerging consensus in the literature demonstrating CO2 and H2O dynamics following large scale disturbance events are dependent not only on tree mortality but also on the remaining and new vegetation responses because mortality and recovery occur at the same time.